You use data structures (struct) to store the individual variables, and
then you can write the entire structure to a file. These data files are
usually written in binary, so you should have a hex editor to look at the
file after you write it to make sure it was written correctly when
debugging it.

For Win32, you can use the CreateFile, ReadFile, WriteFile functions.
For Dos, you can use the open, read, write functions.

Haze

Off the top of my head you can do something like this:

typedef struct _tagData {
int Blah;
int BlahBlah;
float BlahBlahBlahBlah;
} Data;

Data somedata;
char *ptr;

FILE * fp = fopen("datfile.dat", "wb");
if (fp == NULL) {
printf("File system barfed\n");
exit(0);
}

ptr = (char *)&somedata
for (i=0; i < sizeof(Data); i++) {
fputc(fp, *ptr);
ptr ++;
}

fclose(fp);

With more structures just do more fputc loops. With an array of data structures use (sizeof(Data) * num_elements) for the loop counter.

Yes, this was my biggest problem when I first dealed with file formats. I was under the impression that there was something special about disk files, and that the file format really mattered. It really helps to realize that a file, whether it be for game data, a level, a saved game, or anything else is just a collection of bytes, almost just like variables in memory. For example, you have a struct, or a collection of structs that you store your level data in so you can read it and manipulate it in the game. If you want to load or save that level data, you just write that level data to a file, or read it from a file into a variable. Since that was probably confusing, it''s like this

struct Level{// ...};void SaveLevel(Level level){OpenFile(LevelFileName);SaveToFile(level,LevelFileName);CloseFile(LevelFileName);} 

and the same for LoadLevel except with loading, not saving. All you are really doing is storing your variables for later access on the disk. You might save an integer (4 bytes), then a char (1 byte), then a 20-byte string, then a short (2 bytes) and you would read them back in in the same order.

I know I just rambled on, probably needlessly, but I was just trying to get across the point that any data files, or any other file format you create, is just copying your variables to disk or loading them from disk, and the file format is only the order you copy that data in. If you don''t understand what I just said (I don''t know if it was actually clear) you can email me...



------------------------------
Jonathan Little
invader@hushmail.com
http://www.crosswinds.net/~uselessknowledge